The present invention is directed to a method and apparatus for combining communication beams in a wireless communication system. More specifically, the present invention provides an arrangement whereby multiple received signals are weighted and combined to produce an optimally combined communication signal.
Wireless communication has been an area of increased growth over the last decade. In many instances, wireless communication is considered synonymous with mobile cellular communication which has evolved from providing voice only communications to making available voice and data communications along with a myriad of services related to both voice and data. It has also been determined that wireless communications provide an opportunity for establishing access into a communications network from a fixed location such that existing wire line communications can be bypassed. For instance, it has been suggested that a so-called fixed wireless service may provide the opportunity for communication service providers to access users at their home and thereby provide local area service similar to that presently provided by wireline local exchange carriers (LECs). In a fixed wireless system, it is envisioned that a transceiver device would be mounted on a building or dwelling and that each of the transceivers within a particular geographic area would communicate over the air with a given base station, much in the same way that mobile stations passing through a particular cell in a mobile communications environment communicate with the base station servicing that cell. An example of a fixed wireless system in which this communication technique is used is illustrated in FIG. 1. The system includes a base station 10 and a plurality of terminal stations 20, 21 and 22. These terminal stations may be fixed to a building or dwelling and are positioned within a particular distance range from the base station so as to enable wireless communications between the base station and the respective terminal stations.
One issue that is very significant in establishing the appropriate elements for the system relates to the extent to which the terminal station and base station in a given service area can communicate with low error rates or high signal-to-noise ratios. One technique for improving the communications between terminal stations and the base station is to provide an optimally positioned antenna structure for the terminal station. The structure can be particularly oriented with regard to the base station. The antenna structure is optimally positioned so as to exchange signals with the servicing base station. As one would expect, however, it is time consuming and labor intensive to install a fixed antenna that is positioned so precisely as to maximize the capture of signals from the base station and to improve signal-to-noise ratio. It would be beneficial if another technique was available so as to maximize the capture of signals by the antenna, yet selectively process those signals so as to optimally combine the radiation beams communicated between the base station and the terminal station. This would improve the signal-to-noise ratio for communications between those two elements.
The present invention provides a technique for optimally combining the communication beams between two wireless communication terminals. In the embodiment more specifically described, these terminals constitute a base station and a terminal station in a fixed wireless environment. Other wireless terminals may constitute the end points of such a communication system; for example, antennas in a satellite communication system could similarly profit from the beam combination technique of the present invention.
In that beam combination technique, a plurality of antennas receive or capture signals transmitted from the other station. A plurality of beams are then produced from the captured signals. A switch network selectively designates one of the beams to be processed by a primary receiver and some subset of the remaining beams to be processed by secondary receivers. A digital signal processor then weights the signals produced by the primary receiver and the secondary receiver(s) and combines the weighted signals in a manner to enhance the signal-to-noise ratio along the path between the two stations in question.